The present invention relates generally to battlefield personnel threat detection systems. More specifically, the present invention relates to a micro-doppler laser radar (ladar) battlefield personnel threat detection system for detecting and localizing threats to deployed personnel. According to one aspect of the present invention, the micro-doppler ladar system detects the principal threat to deployed field personnel, i.e., deployed enemy personnel. A method for employing a micro-doppler ladar system for detecting and localizing threats to deployed personnel is also disclosed.
The future battlefield will demand an increased ability to acquire, transmit, process, disseminate, and utilize surveillance and target acquisition information. One relatively new source of intelligence information is remote monitoring of the battlefield, using seismic, acoustic, and magnetic remotely monitored sensors (REMS). When enemy personnel or vehicle movement activates these remote sensors, a monitor display located behind friendly lines indicates the type of activity. The operator can derive from this display not only the enemy's presence but also such information as direction and/or speed of convoys and personnel, number of the vehicles in a convoy, and convoy composition, e.g., armored versus wheeled vehicles. REMS works on the principles of detection of an outside stimulus, logic processing of that stimulus, and transmission of a coded signal to a readout device. The tactical unattended ground sensors used by REMS may include sensors which operate on magnetic, seismic, acoustic, electromagnetic and audio detection principles. It will be appreciated that the REMS approach to perimeter monitoring requires the initial placement of several REMS, for example, geophones. Manual placement of these geophones requires use of the very personnel that REMS is intended to protect; remote placement by air drops or artillery generally alerts enemy forces to the fact that an opposing force is interested in a specific segment of the theater.
Another attempt at providing effective perimeter protection for deployed personnel involves a detection system which detects intruders using a transmission line, for example, a Goubau line, as a sensing element. The transmission line is positioned about the perimeter of the area to be protected and an antenna applies pulsed RF energy to the line. An intruder in the field of the line causes an RF reflection back toward the source, which reflection is detected by Doppler range-gating techniques. As with the geophone system mentioned above, the installation of the transmission line detection system dictates that deployed personnel be placed at risk to physically lay the transmission line.
The ability to detect the presence of an enemy soldier or hostile individual concealed within a structure, i.e., within a building or vehicle, or behind a barrier such as vegetation, can be of paramount importance both to soldiers in combat conditions and to law enforcement officials in tactical situations. For example, the detection thresholds for uniformed human targets have been established in field tests as varying between 50 and 115 feet in a semi deciduous tropical forest, with the longer detection threshold being observed near the end of the dry season when less foliage is present. The use of optical devices such as non magnifying yellow, red, and dichroic lenses as aids to personnel detection in a tropical forest has been determined to be ineffective. Although detection of hostile personnel within buildings and vehicles is possible using infrared detectors, the effectiveness of such devices varies with ambient conditions and is inversely proportional to the amount of thermal insulation provided by, for example, the building.
The consequences of failing to detect individual(s) such as illegal aliens concealed in a vehicle, a terrorist holed up in a room in a building, or a group of enemy soldiers hiding in vegetation around a landing zone, in a timely manner, can range from serious to catastrophic. Moreover, knowledge regarding the physiological status, e.g., is the target aware of detection or in a state of heightened alert, of these individuals could also be invaluable in combat and/or tactical situations. There are no conventional systems that can provide such information reliably.
It will be appreciated that such a system capable of detecting, for example, enemy soldier approaching through thick vegetation, could likewise be used monitor to the physiological state of an individual remotely. Moreover, such a postulated system could be invaluable in determining, e.g., whether a witness is lying to Congress or a court, whether a suspicious individual in a crowd or audience is likely to be a terrorist or assassin, whether a potentially suicidal person is about to jump, or whether an adversary across a bargaining table is calm or excited. No transportable system presently exists which can provide remote detection of a person's physiological status.
The problem of detecting people in hiding from a distance is central to developing reliably effective methods of countering ambushes in military operations. Techniques that depend upon detection of airborne human effluents are among those that have been considered. However, the equipment needed to identify chemical clouds or plumes which signal potential hazzards to friendly personnel has heretofore not been available. Although a CO.sub.2 MTI Laser Radar for Personnel and Vehicular Detection project, whose primary goal was the construction of a feasibility model which could be tripod mounted, easily transported in the field, and yet withstand the rigors of field use without performance degradation, was initiated, the laser radar finally deployed consisted of two heavy, bulky units; a laser radar head; and power supply/control panel. Such units were never considered successful because the rigid structure of the CO.sub.2 laser and its relatively cumbersome power supply, i.e., field generator, made the system transportable, not portable. It will be appreciated that the fixed frequency output wavelength of the CO.sub.2 laser radar further limited the usefulness of the system.
What is needed is a system for detecting the presence of a threat to an individual based on measurement of an immutable characteristic of the threat. Moreover, what is needed is a system for detecting the presence of antagonist individuals who pose a threat to deployed soldiers or law enforcement officers. What is also needed is a system for sensing the physiological status of individuals classified as threats to friendly forces.